Improved momentum exchange theory for incompressible regenerative turbomachines

On the basis of the momentum exchange theory, an improved mathematical model is developed to analyse the complicated helical flow in regenerative turbornachines and to suggest a systematic way to design such kind of machines. The helical flow in the machines is resolved into a peripheral component and a circulatory component, and a theoretically sound method is proposed to calculate the circulatory flow velocity and slip factor, which are closely related to the machine performance. To implement the present method, the concepts of a circulatory pivot and an effectiveness of the circulatory flow are introduced. The circulatory flow loss was successfully estimated by introducing a bend-combination factor by adding four right angle bends losses. It was found that the overall head rise and the hydraulic efficiency can be accurately predicted by the proposed model equation and the present loss models. Development of the static pressure along the peripheral direction could be predicted satisfactorily.